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The Sichuan-Tibet railway construction has received significant attention from both China and abroad. The new section from Ya'an to Nyingchi is about 1018.6 km long, including 69 tunnels with a total length of 841.7 km. The longest tunnel (Yigong tunnel) is 42.4 km long. The successful construction of the Sichuan-Tibet railway depends largely on tunnel construction. Due to the complex conditions, tunnel construction for the Sichuan-Tibet railway poses great challenges to the research community. This paper aims to illustrate the necessity of interdisciplinary and joint research to solve problems associated with tunnel construction that will be encountered in the immediate future and facilitate the communication and exchange of ideas between disciplines. To this end, based on a systematic analysis of the available data related to Sichuan-Tibet railway tunnels, six major aspects of the geology, environment, and engineering conditions are identified. Next, based on the engineering responses from the Sichuan-Tibet railway tunnels, potential technical problems and risk characteristics are predicted and evaluated. Further, six key scientific issues are identified and discussed based on a coupled multi-layer analysis of essential tunnel engineering issues. Finally, research directions, technical ideas, and research methods that should be carried out for this project are proposed. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) nanosheets have drawn great attention because of their interesting electronic and chemical properties since the isolation of graphene in 2004. This book chapter would summarize recent advances in the electrochemical oxygen-relative reactions, such as oxygen reduction reaction and oxygen evolution reaction by using electrocatalysts of graphene and its derivatives and also other 2D materials. From the mechanistic point of view, the link between structure and activity of these 2D nanosheets is discussed. Strategies that are effective to adjust electronic structure in these 2D materials and thereby catalytic activities are emphasized. Future opportunities and challenges in this field are outlined. [ABSTRACT FROM AUTHOR]

Heterogeneousreactions of NO2on various mineral aerosolparticles have been investigated in many previous studies, but a fundamentalunderstanding of how the adsorption of formaldehyde influences theheterogeneous reactions of NO2remains unclear. In thiswork, the effect of formaldehyde preadsorption on heterogeneous reactionof NO2on the surface of γ-Al2O3at 298 K and ambient pressure was investigated by using diffusereflectance infrared Fourier transform spectrometry (DRIFTS). It wasfound that the preadsorption of HCHO on γ-Al2O3could suppress the formation of nitrate, and the rate ofnitrate formation decreased with increasing amount of preadsorbedHCHO, whereas the following heterogeneous uptake of NO2could suppress the hydration reaction of HCHO and promote the productionof HCOO–during the reaction. Surface nitrite wasformed and identified to be an intermediate product and graduallydisappeared as the reaction proceeded. The amount of the formed nitritedecreased when the amount of HCHO increased. Uptake coefficients ofheterogeneous reactions were calculated and found to be sensitiveto the adsorption of HCHO. A possible mechanism for the influenceof HCHO adsorption on the heterogeneous conversion of NO2on γ-Al2O3was proposed, and atmosphericimplications based on these results were discussed. [ABSTRACT FROM AUTHOR]

The carbon-coated TiO2(B) nanosheet composite synthesized by one-step hydrolysis of TiCl3 followed by vacuum annealing and air annealing delivers outstanding electrochemical performance as a negative electrode for Li-ion batteries, i.e. reversible capacity above 150 mA h g-1 at 30 C (10 A g-1). [ABSTRACT FROM AUTHOR]

A universal strategy was developed for the preparation of high-temperature-stable carbon nanotube (CNT) -supported metal nanocatalysts by encapsulation with a mesoporous silica coating. Specifically, we first showed the design of one novel catalyst, Pt@CNT/SiO2, with a controllable mesoporous silica coating in the range 11−39 nm containing pores ≈3 nm in diameter. The hollow porous silica shell offers a physical barrier to separate Pt nanoparticles from contact with each other, and at the same time the access of reactant species to Pt was not much affected. As a result, the catalyst showed high thermal stability against metal particle agglomeration or sintering even after being subjected to harsh treatments up to 500 °C. In addition, degradation in catalytic activity was minimized for the hydrogenation of nitrobenzene over the catalyst treated at 300 °C for 2 h. The scheme was also extended to coat porous silica onto the surfaces of CuRu@CNT and the resultant catalyst thereby can be reusable at least four times without loss of activity for the hydrogenolysis of glycerol. These results suggest that the as-prepared nanostructured CNT-supported catalysts may find promising applications, especially in those processes requiring rigorous conditions. [ABSTRACT FROM AUTHOR]

In this paper, we report a method for nonuniform data-dependent noise prediction (DDNP), in which the noise predictive filters do not have an identical order (number of taps). To accommodate this new architecture, we implemented a partial decision feedback strategy for branch metric computations of the higher order predictive filters. Theoretical analysis and computer simulations show that our proposed DDNP can achieve a better tradeoff between detection performance and computational complexity compared with the previously reported DDNP. [ABSTRACT FROM AUTHOR]

ZrO2−carbon nanotube (CNT) composites have been successfully synthesized via decompositoin of Zr(NO3)4·5H2O in supercritical carbon dioxide−ethanol solution with dispersed CNTs at relatively low temperatures. The samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analyses. It was demonstrated that CNTs were fully coated with an amorphous ZrO2layer, and the coating layer was nominally complete and uniform. In addition, the thickness of the coating sheath could be readily controlled by tuning the Zr(NO3)4·5H2O/CNTs ratio used. Furthermore, the chemiluminescent sensor prepared from ZrO2−carbon nanotube composites exhibited dramatic sensitivity as well as high stability and selectivity to ethanol. [ABSTRACT FROM AUTHOR]

In order to improve the automatic planning and adaptive scheduling ability of sailing route and guide the management of sailing route, an optimal path planning model based on fuzzy neural network is proposed. The control instruction information of sailing route planning is extracted by using wireless sensor networking information scheduling technology, and the sailing route planning is carried out by combining the network information recognition and pattern scheduling of sailing route at sea. The statistical big data is extracted, the fuzzy scheduling of the associated feature set after information sampling is carried out, and the fuzzy neural network control technology is used to automatically screen and optimize the route of sailing route planning at sea. The information management platform of the Internet of things is constructed to carry out the automatic planning and distributed cooperative scheduling of the sailing route at sea, and the statistical data of the route planning of the sailing ship collected by all the member nodes are evenly configured in the cluster of things. The fuzzy PID neural network learning method is used to plan the sailing route of marine sailboat, and the distributed cooperative scheduling of sailing route planning is realized according to the result of automatic optimization. The simulation results show that the system can effectively realize the automatic planning and optimal scheduling of sailing route, and the reliability of route planning is high and the convergence is good. [ABSTRACT FROM AUTHOR]

Rock load on lining structures increases over time for tunnels buried in rheological rock, and in addition deterioration of primary lining is common due to its structural characteristics and service environment attack, where these delayed features affect the mechanical response of tunnels. However, accounting for these delayed features in long-term stability assessment of tunnel structures is complex and has not attracted enough attention. In this paper, an analytical approach is proposed for investigating long-term mechanical response of tunnel structures in rheological rock influenced by degradation of primary lining. For this purpose, degradation of primary lining, characterized by decreasing concrete stiffness over time, is quantitatively described by an exponential model. The rheological characteristic of surrounding rock is simulated by the Burgers model. The time-varying solutions for rock deformation and support pressure are obtained by considering the coordinated interaction between surrounding rock and linings, and their correctness is verified by comparing them with numerical results. The results revealed that the pressure imposed on linings due to the rheological behavior of surrounding rock increases over time. As the primary lining degrades, the rheological load is transferred from primary lining to secondary lining, leading to increasing pressure on secondary lining; and a faster degradation rate of primary lining leads to greater pressure on secondary lining. Therefore, the primary lining should not be overlooked in long-term safety assessment of operation tunnels because of its role in bearing and transmitting load. Finally, the tunnel's design and operational maintenance strategy are discussed when the delay effects of surrounding rock and lining are taken into account. [ABSTRACT FROM AUTHOR]

Four organic amine-based solvents were discovered which enable direct exfoliation of graphite to produce high-quality and oxygen-free graphene nanosheets. These solvents outperform previously used solvents and additives such as N-methyl-pyrrolidone and surfactants in terms of their dispersing capacity. The resulting dispersions allow the facile fabrication of zeolitic imidazolate frame-work (ZIF)--graphene nanocomposites with remarkable CO2 storage capability. [ABSTRACT FROM AUTHOR]

Discovering stabilizers that protect phosphorene from oxidative degradation is critically required for dispersion processing of black phosphorus (BP). It is equally important to also find environmentally friendly, low-cost, and practical exfoliating media. Herein, we demonstrate the yield of remarkably stable phosphorene by coating with a polymer to shield the nanosheets from reaction with water and air. The polymer shell suppresses the rate of BP degradation more efficiently than previously reported systems. We present for the first time a simple kinetic model for exfoliation of BP in polyvinylpyrrolidone (PVP) ethanol solution that appears to quantitatively fit BP exfoliation data, and it illuminates mechanistic aspects of exfoliation. Exfoliated flakes consist of a high level of 51% crystalline single layers that are free from structural disorder or oxidation. A successive centrifugation and redispersion strategy is developed affording dispersions with high phophorene-to-stabilizer ratio, which is very useful for further applications. We also demonstrate that PVP-stabilized phosphorene dispersions possess saturable absorption at both 515 and 1030 nm, which have potential use as ultrafast broadband absorbers. Furthermore, such phosphorene dispersions were processed to prepare new metal/phosphorene nanocomposites that have potential for use as electrocatalysts in electrolytic cells. [ABSTRACT FROM AUTHOR]

Coastal hypoxia is an increasingly recognized environmental issue of global concern to both the scientific community and the general public. We assessed the relative contributions from marine and terrestrially sourced organic matter that were responsible for oxygen consumption in a well-studied seasonal coastal hypoxic zone, the East China Sea off the Changjiang Estuary. Our fieldwork was conducted in August 2011 during reinstatement of a subsurface hypoxia, when we observed a continuous decline of dissolved oxygen along with production of dissolved inorganic carbon resulting from organic carbon remineralization. On the basis of a three end-member mixing model and determinations of the stable isotopic compositions of dissolved inorganic carbon (δ13CDIC), the end product of particulate organic carbon (POC) degradation, we quantified the δ13C value of the remineralized organic carbon (δ13COCx), which was -18.5 ± 1.0%º. This isotopic composition was very similar to the δ13C of marine sourced POC produced in situ (--18.5 ± 0.3%º) rather than that of the terrestrially sourced POC (--24.4 ± 0.2%º). We concluded that marinesourced organic matter, formed by eutrophication-induced marine primary production, was the dominant oxygen consumer in the subsurface hypoxic zone in the East China Sea off the Changjiang Estuary. [ABSTRACT FROM AUTHOR]

The Yellow River is the second largest river in China. Carbon transport by the Yellow River has significant influence on riverine carbon cycles in Asia. In order to monitor seasonal and spatial variations of carbon concentrations and to estimate carbon exports, water and suspended solids were sampled every 10 days at three representative stations (Qingtongxia, Tongguan, and Luokou) along the mainstream of the Yellow River. Results showed that riverine carbon was mainly in dissolved form, except during flood period and water and sediment regulation (WSR) scheme, when particulate organic carbon (POC) dominated. Concentration of dissolved inorganic carbon was mostly 5 to 10 times higher than that of dissolved organic carbon (DOC). DOC was mainly related to a natural process (leaching effect) in the upstream and anthropogenic activities in the midstream (domestic sewage and fertilizer application) and downstream (industrial wastewater). POC was connected with high suspended solids. Annually carbon delivered to the Bohai Sea was 1.34 × 1012 g/yr, accounting for 0.15% of the global total riverine carbon flux. Mean DOC exported accounted for 0.12% of the Asian rivers' DOC flux. WSR played an important role in the carbon transport, which accounted for 1/5 to 1/3 of the corresponding annual fluxes. [ABSTRACT FROM AUTHOR]

The Yellow River is the second largest river in China. Carbon transport by the Yellow River has significant influence on riverine carbon cycles in Asia. In order to monitor seasonal and spatial variations of carbon concentrations and to estimate carbon exports, water and suspended solids were sampled every 10 days at three representative stations (Qingtongxia, Tongguan, and Luokou) along the mainstream of the Yellow River. Results showed that riverine carbon was mainly in dissolved form, except during flood period and water and sediment regulation (WSR) scheme, when particulate organic carbon (POC) dominated. Concentration of dissolved inorganic carbon was mostly 5 to 10 times higher than that of dissolved organic carbon (DOC). DOC was mainly related to a natural process (leaching effect) in the upstream and anthropogenic activities in the midstream (domestic sewage and fertilizer application) and downstream (industrial wastewater). POC was connected with high suspended solids. Annually carbon delivered to the Bohai Sea was 1.34 × 1012 g/yr, accounting for 0.15% of the global total riverine carbon flux. Mean DOC exported accounted for 0.12% of the Asian rivers' DOC flux. WSR played an important role in the carbon transport, which accounted for 1/5 to 1/3 of the corresponding annual fluxes. [ABSTRACT FROM AUTHOR]

Unsupervised synthetic aperture radar (SAR) image segmentation is a fundamental preliminary processing step required for sea area detection in military applications. The purpose of this step is to classify large image areas into different segments to assist with identification of the sea area and the ship target within the image. The recently proposed triplet Markov field (TMF) model has been successfully used for segmentation of nonstationary SAR images. This letter presents a hierarchical TMF model in the discrete wavelet domain of unsupervised SAR image segmentation for sea area detection, which we have named the wavelet hierarchical TMF (WHTMF) model. The WHTMF model can precisely capture the global and local image characteristics in the two-pass computation of posterior distribution. The multiscale likelihood and the multiscale energy function are constructed to capture the intrascale and intrascale dependencies in a random field (X, U). To model the SAR data related to radar backscattering sources, the Gaussian distribution is utilized. The effectiveness of the proposed model for SAR image segmentation is evaluated using synthesized and real SAR data. [ABSTRACT FROM AUTHOR]

Based on in situ hydrographic measurements at a station at about 60 m depth near the local shelf break in July 2011 and a satellite image of the sea-surface roughness, we present the evidence of existence and characteristics of high-frequency internal waves (HIWs) in the southern Taiwan Strait. Variations of the thermohaline structure at the observational site were revealed by repeating conductivity-temperature-depth (CTD) profiling measurements of every 2 hours, while fluctuations of the isothermals due to the passage of HIWs were recorded by continuous CTD measurements with a probe positioned approximately in the middle of the pycnocline. A fast sampling frequency of 8 Hz allows the structure of the HIWs to be captured in great detail. The waves were depression waves, with a period of about 6.2 min and an amplitude of about 25 m. The propagation speed of the waves is estimated to be 0.56 m/s by solving the KdV equation with the observed background stratification. The frequent occurrence of HIWs in the Taiwan Strait is evidenced by the analysis of a MODIS true color image of the sea-surface roughness. The possible generation mechanism of the HIWs is discussed based on a MODIS image and the perturbed KdV equation. [ABSTRACT FROM AUTHOR]

We developed a route to synthesize rutile TiO2nanocrystals (NCs) with the assistance of 1-butyl-3-methylimidazolium chloride (bmim−). The phase transformation from anatase to rutile phase was investigated, and a simple model to describe the phase transformation process was proposed considering that the nucleation and growth of rutile phase were determined by the aggregation manner of anatase NCs and Ostwald ripening process, respectively. It was demonstrated that the surfactant-like nature of the IL used was crucial for controlling the crystallization process via controlling the aggregation manner of the NCs. The phase, shape, and size of TiO2NCs could be tuned by the controlling the operating conditions, such as temperature, solution acidity, and reactant concentration of the bmim−/TiCl4/H2O reaction system. Phase-pure rutile multipods and 1D nanorods with different sizes were controllably obtained. [ABSTRACT FROM AUTHOR]

Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to ∼0.01 mg ml−1, produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent–graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of ∼1 wt%, which could potentially be improved to 7–12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry. [ABSTRACT FROM AUTHOR]

Examines the use of Multiple Displacement Amplification (MDA) to amplify the whole genome generating large amounts of DNA for genetic testing. Analysis of amplification directly from cell lysates; Coverage of the MDA amplification of the human genome; Views of an accurate genotyping from MDA amplified DNA.

Background: Rolling circle amplification of ligated probes is a simple and sensitive means for genotyping directly from genomic DNA. SNPs and mutations are interrogated with open circle probes (OCP) that can be circularized by DNA ligase when the probe matches the genotype. An amplified detection signal is generated by exponential rolling circle amplification (ERCA) of the circularized probe. The low cost and scalability of ligation/ERCA genotyping makes it ideally suited for automated, high throughput methods. Results: A retrospective study using human genomic DNA samples of known genotype was performed for four different clinically relevant mutations: Factor V Leiden, Factor II prothrombin, and two hemochromatosis mutations, C282Y and H63D. Greater than 99% accuracy was obtained genotyping genomic DNA samples from hundreds of different individuals. The combined process of ligation/ERCA was performed in a single tube and produced fluorescent signal directly from genomic DNA in less than an hour. In each assay, the probes for both normal and mutant alleles were combined in a single reaction. Multiple ERCA primers combined with a quenched-peptide nucleic acid (Q-PNA) fluorescent detection system greatly accellerated the appearance of signal. Probes designed with hairpin structures reduced misamplification. Genotyping accuracy was identical from either purified genomic DNA or genomic DNA generated using whole genome amplification (WGA). Fluorescent signal output was measured in real time and as an end point. Conclusions: Combining the optimal elements for ligation/ERCA genotyping has resulted in a highly accurate single tube assay for genotyping directly from genomic DNA samples. Accuracy exceeded 99 % for four probe sets targeting clinically relevant mutations. No genotypes were called incorrectly using either genomic DNA or whole genome amplified sample. [ABSTRACT FROM AUTHOR]

Examines the comprehensive human genome amplification using multiple displacement amplification. Availability of genomic DNA for adequate quality and quantity; Development of methods for whole genome amplification; Analysis on the restriction fragment length of polymorphism and DNA sequencing.

Background: Single nucleotide polymorphisms (SNPs) are the foundation of powerful complex trait and pharmacogenomic analyses. The availability of large SNP databases, however, has emphasized a need for inexpensive SNP genotyping methods of commensurate simplicity, robustness, and scalability. We describe a solution-based, microtiter plate method for SNP genotyping of human genomic DNA. The method is based upon allele discrimination by ligation of open circle probes followed by rolling circle amplification of the signal using fluorescent primers. Only the probe with a 3' base complementary to the SNP is circularized by ligation. Results: SNP scoring by ligation was optimized to a 100,000 fold discrimination against probe mismatched to the SNP. The assay was used to genotype 10 SNPs from a set of 192 genomic DNA samples in a high-throughput format. Assay directly from genomic DNA eliminates the need to preamplify the target as done for many other genotyping methods. The sensitivity of the assay was demonstrated by genotyping from 1 ng of genomic DNA. We demonstrate that the assay can detect a single molecule of the circularized probe. Conclusions: Compatibility with homogeneous formats and the ability to assay small amounts of genomic DNA meets the exacting requirements of automated, high-throughput SNP scoring. [ABSTRACT FROM AUTHOR]

We demonstrate a facile and versatile method to grow Ru particles uniformly on pristine few-layer graphene (FLG) in supercritical diethylamine. In particular, a large number of Ru subnanometer clusters less than 1.0 nm were observed. The particle size can be tuned by manipulating the loading content of Ru and controlling the reaction temperature. The resulting Ru/FLG showed remarkably high activity, selectivity, and reusability towards the hydrogenation of levulinic acid to γ-valerolactone. This method is flexible, and can be extended to the synthesis of a variety of other ultrafine metal particles supported on FLG. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction (ECR) offers an important pathway for renewable energy storage and fuels production. It still remains a challenge in designing highly selective, energy-efficient, robust, and cost-effective electrocatalysts to facilitate this kinetically slow process. Metal-free carbon-based materials have features of low cost, good electrical conductivity, renewability, diverse structure, and tunability in surface chemistry. In particular, surface functionalization of carbon materials, for example by doping with heteroatoms, enables access to unique active site architectures for CO2 adsorption and activation, leading to interesting catalytic performances in ECR. We aim to provide a comprehensive review of this category of metal-free catalysts for ECR, providing discussions and/or comparisons among different nonmetallic catalysts, and also possible origin of catalytic activity. Fundamentals and some future challenges are also described. [ABSTRACT FROM AUTHOR]

The article focuses on a method that can use an in situ redox reaction between the reductive titanium oxide support and metal salt precursors in aqueous solution to grow noble metal particles on titania. According to the authors, the method does not require extra reducing agent and can be operated under mild conditions. They concluded that the method can introduce a new approach to prepare metal supported composites.